We have proposed to identify restriction fragments of EBV DNA that contain the origin of lytic viral DNA replication or of latent viral DNA replication. D98/HRI cells that carry P3HRI EBV genomes and grow in monolayer will be induced for viral DNA replication by IUDR and transfected with bacterial plasmid containing Amp(r), TK and viral DNA fragment but lacking sequence inhibitory to mammalian DNA replication. The plasmid with EBV fragment that can replicate together with P3HR viral DNA will be identified. D98/Raji TK- cells will be transfected with the same plasmid DNA with EBV DNA fragmetn and the fragments that can persist in D98/Raji cells will be identified. The region for the origin of viral DNA replication will be reduced to minimum necessary size by restriction enzymes, Bal 31 and/or DNAase 1 pratial digestion. If the plasmid containing the origin of latent viral DNA replication cannot persist in D98 cells that do not carry viral genome, then viral DNA fragments that provide functions for the plasmid DNA to persist in D98 cells will be identified. Finally celular DNA sequences hybridizable to the origin of latent viral DNA replication will be examined, based on an assumption that latent viral plasmid DNA and cellular DNA might share similar sequence for the origin of DNA replication.